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Biomedical subjects

A Nagy

Publications and source records attributed to A Nagy.

At least 289 records · Page 16Linked to original sources
PubMed1984

Beta-adrenergic and muscarinic cholinergic receptors: overlap in their genetic determination.

Significant positive correlation between the ligand binding values for beta-adrenergic receptors and those for muscarinic cholinergic receptors was found in five inbred strains of mice (r = 0.84) and in different vertebrate species (r = 0.99). Comparative analysis of analogous receptor studies done on various brain regions in other laboratories revealed high positive correlation between regional binding values for these two receptors. In conjunction with the work presented here, an overlap in the genetic determination of beta-adrenergic and muscarinic cholinergic receptors is suggested.

Animals↗
PubMed1984

Comparative studies with somatostatin and cysteamine in different behavioral tests on rats.

In the present study the effects of somatostatin and cysteamine (a selective decreaser of the somatostatin level in the body) were compared in different behavioral tests on rats. Somatostatin inhibited the extinction of active avoidance behavior 8 hr and 24 hr after intracerebroventricular (ICV) treatment, while cysteamine facilitated it 4 hr and 8 hr after subcutaneous (SC) treatment. Somatostatin did not significantly influence the cysteamine-induced facilitation of the extinction. Somatostatin did not have a significant effect on T-maze spatial discrimination learning and reverse learning, whereas cysteamine markedly attenuated the performance 4 hr (1st day) after treatment. Somatostatin in a dose of 4 micrograms (ICV) increased the locomotor activity 10 min after treatment, while cysteamine markedly decreased all parameters of the open-field test. These effects of the drug had disappeared 24 hr after treatment. If different doses of somatostatin (4 micrograms or 10 micrograms ICV) were administered to cysteamine-pretreated rats, the peptide did not modify the drug-induced changes in the open-field test. The data suggest that the brain somatostatin might have a physiological role in the organization of certain types of behavior.

Animals↗
PubMed1984

Polymorphism and inheritance of serum esterases and beta-globulins in the paradise fish (Macropodus opercularis; Anabantidae).

Electrophoretic variants of serum esterases and beta-globulins in two subspecies of paradise fish (Macropodus opercularis) were studied. Four esterase loci (Est-1, Est-2, Est-3 and Est-4), a single transferrin (Tf) and another major beta-globulin locus (Bg) were identified by segregational analysis. Est-3 seems to be a monomorphic locus. Three alleles of Est-1, two of Est-2, two of Est-4, four of Tf and two alleles of Bg were found in the laboratory population. None of these loci were closely linked. Electrophoretic patterns of F1 hybrids confirmed the monomeric structures of each of the studied proteins. Allelic segregation at the Tf and Bg loci was normal in F2 and backcross populations. In crosses of the two Macropodus subspecies there were deviations from Mendelian ratios because of missing recombinant esterase phenotypes. Each of these would have been homozygous Est-2f/f. We suppose that Est-2f/f causes lethality in the early phase of development, except in the Est-1c/c, Est-2f/f combination characteristic of the parental subspecies M.o. concolor.

Alleles↗
PubMed1984

Rapid preparation of synaptosomes from mammalian brain using nontoxic isoosmotic gradient material (Percoll).

A new procedure is described for the isolation of synaptosomes from various parts of mammalian brain. This method utilizes an isoosmotic Percoll/sucrose discontinuous gradient and has some advantages over the traditionally used synaptosomal isolation techniques: (1) it is possible to prepare suitable gradients while retaining isoosmolarity; (2) the time of the preparation is remarkably short (approximately 1 h); (3) if necessary, the gradient material can be easily removed from the samples. Intact synaptosomes were recovered from the 10%/16% (vol/vol) Percoll interphase. The fractions were identified and characterized by electron microscopy and by several biochemical markers for synaptosomes and other subcellular organelles. The homogeneity of the preparations is comparable to or better than that of synaptosomes prepared by the conventional methods. This procedure has been successfully used for the isolation of synaptosomes from very small tissue samples of various experimental animals and human brain.

Animals↗
PubMed1984

A freeze-fracture study of ruffle-ended post-secretory ameloblasts.

The post-secretory portion of the rat incisor enamel organ was prepared for routine transmission electron microscopy and freeze-fracture replication in order to define further the structural surface features of the ruffle-ended ameloblasts. Surface views of the distal plasma membrane of the ruffle-ended ameloblasts revealed a well-developed zonula occludens junction with from six to ten rows of tight junctional strands. Gap junctions were also observed just proximal to the tight junctional strands. The membranes of the ruffled border contained a rich supply of intramembrane particles (IMP). The IMPs were approximately 7 to 8 nm in diameter and preferentially located on the P-face profiles of the membrane. The density of IMPs on the membranes of the ruffled border was higher than that on the lateral borders of the cell. It is suggested that the IMPs of the ruffled border may represent enzymatic proteins in the basal cell membrane of absorptive ameloblasts. In addition, the large, highly-developed zonula occludens appeared structurally capable of sealing the intercellular spaces between the ruffle-ended ameloblasts.

Ameloblasts↗
PubMed1983

Met-enkephalin binding to opiate receptors is not functionally coupled to biodegradation.

Using synaptosomal rat brain membranes, the degradation of Met-enkephalin in both free and receptor-bound form was measured, together with the dissociation of Met-enkephalin from the receptors. The results show that the degradation rate of initially receptor-bound Met-enkephalin is significantly smaller than either the rate of dissociation from the receptors or that of the degradation of free Met-enkephalin. These data suggest that intact Met-enkephalin dissociates from the receptors and then it becomes a target for the same membrane-associated peptidases that split free Met-enkephalin. This view is supported by the good fitness of the measured degradation of initially receptor-bound Met-enkephalin to the predicted degradation curve calculated from the dissociation rate of receptor-bound Met-enkephalin and the degradation rate of free Met-enkephalin.

Animals↗
PubMed1983

Solubilization and separation of divalent cation dependent adenosinetriphosphatase in native gradient polyacrylamide slab gel.

A new method for the simultaneous solubilization and separation of different cation dependent adenosinetriphosphatases after non-denaturing polyacrylamide gel electrophoresis is described. Using a gradient system, 3 distinct divalent cation dependent adenosinetriphosphatase bands (Mg2+-, Ca2+-, and Mg2+ + Ca2+-dependent) could be separated on the same gel from NP-40 solubilized brain microsomal preparations. This indicates that these 3 adenosinetriphosphatases represent distinct molecular species.

Animals↗
PubMed1983

Thyroid hormones and derivatives inhibit flunitrazepam binding.

Thyroid hormones and their derivatives were found to inhibit [3H]flunitrazepam binding stereospecifically and in a monophasic manner. Among the compounds tested, D-thyroxine was the most potent inhibitor (IC50 = 0.5 microM). The naturally occurring L-thyroxine was about 40-fold less potent (IC50 = 20 microM). The structure-activity relationships seem to imply that the thyronine base has the principal role in the inhibition of benzodiazepine receptor binding. The type of inhibition was examined with the most potent inhibitor, D-thyroxine, by Scatchard analysis. The apparent dissociation constant (KD) of the [3H]flunitrazepam binding increased and the receptor density (Bmax) decreased as a function of D-thyroxine concentration; this is characteristic of mixed-type inhibition.

Animals↗
PubMed1983

Adenosine triphosphatase activity at the external surface of chicken brain synaptosomes.

An ATP-hydrolysing activity on the external surface of intact synaptosomes from chicken forebrain has been investigated. The observed ATPase activity was not due to leakage of the intracellular ATPase activities, of artefacts resulting from breakage of the nerve endings during the incubation and isolation periods, or to possible contamination by other subcellular particles. Disruption of the synaptosomes resulted in an approximately 2.5-fold increase of the basal, Mg2+-dependent ATPase activity, suggesting that the plasma membrane was acting as permeability barrier to the substrate. ATP hydrolysis was maximal (0.8 mumol Pi/min/mg protein) at pH 8.2 in a medium containing either Mg2+ or Ca2+ ions. Ouabain (0.2 mM) and oligomycin (2 micrograms/mg protein) had no appreciable effect on this ATPase activity. Kinetic studies of the enzyme revealed an apparent Km value of ATP of approximately 4 x 10(-5) M. These data are consistent with the view that the observed ATP hydrolysis was being catalysed by an ectoenzyme, i.e., an enzyme in the plasma membrane of the nerve endings with its active site facing the external medium. The rapid hydrolysis of the released ATP is a suspected function for this ecto-ATPase.

Adenosine Triphosphatases↗
PubMed1983

Characterization of a protein kinase from chicken oviductal fluids.

Protein kinase has been found extracellularly in avian oviductal secretions. The enzyme has been isolated and shown to be primarily type II cAMP enhanced. The Ka for cAMP activation, binding and elution from ion-exchange columns, molecular weight of subunits, pH optimum as a histone kinase, response to cations, kinetic properties, and preference for lysine-rich histone are similar to those of mammalian type II protein kinase. Gel filtration data suggest that the dimer form is the functional entity in the reproductive tract. The catalytic subunit has been purified to greater than 90% homogeneity and has a Km of 4 mumol/l and Vmax of 10(6) U/mg, comparable to published values for bovine catalytic subunit.

Animals↗